A standard bed construction that has been popular for some time includes a frame for supporting a box spring. The box spring, in turn, is designed to support a mattress. Mattresses are available in a variety of sizes and are also constructed in various ways. One such construction that has proved to be highly desirable includes the use of an innerspring having a plurality of discrete coil springs, which can be encapsulated in individual fabric pockets joined together in a string. An assembly of this type is commonly known as a Marshall construction. Once the strings of coils are formed, they may be arranged, for example, in a chevron or other pattern to provide an innerspring assembly in which the individual springs have longitudinal axes oriented parallel one to another and the springs are closely packed together in an array having a generally rectangular shape in plan with the ends of the springs lying in a common plane. A suitable quilted foam pad may then be used to cover the innerspring and provide a generally planar surface on which a person can sleep. Preferably, the innerspring is covered on both sides and has fabric edging connecting the opposed surface covers, thereby defining a unitary mattress assembly.
Conventionally, each spring is manufactured from a single, solid, coiled steel wire. The spring characteristic is defined, for example, by the wire size and spring dimensions (pitch, coil length, coil diameter, etc.), which can be selected according to the desired properties of the seating or resting surface of the article of furniture or mattress in a manner known in the art.
One disadvantage in the above described conventional solid wire spring construction is that steel that is suitable for this type of spring can be costly. Another disadvantage is that if one or more of the springs malfunction (e.g., break), the seating and/or sleeping comfort of the seating or resting surface is impaired. Therefore, it would be desirable to provide a spring construction that is less expensive to manufacture than a solid wire spring, and that retains or improves upon the performance characteristics of the solid wire spring.